1. Field of the Invention
The present invention relates to an external light shielding film and an optical filter for a display apparatus having the same, and more particularly, to an external light shielding film and an optical filter for a display apparatus having the same in which a contrast ratio in a bright room is increased, and a color varies depending on ON/OFF of the display apparatus.
2. Description of the Related Art
As modern society becomes more information oriented, technology of parts and devices related to image displays is remarkably advancing, and these parts and devices are becoming widespread. Display apparatuses utilizing parts and devices related to photoelectronics are becoming significantly widespread and used for television apparatuses, monitor apparatuses of personal computers, and the like. Also, display apparatuses are becoming both larger and thinner.
Plasma display panel (PDP) apparatuses are generally gaining popularity as next-generation display apparatuses to simultaneously satisfy a trend of becoming larger, and of becoming thinner, when compared with cathode-ray tubes (CRTs) representing existing display apparatuses. The PDP apparatuses display images using a gas discharge phenomenon, and exhibit superior display characteristics such as display resolution, brightness, contrast ratio, an afterimage, a viewing angle, and the like. Also, since the PDP apparatuses are generally seen as having the most appropriate characteristics for future high-quality digital televisions due to thin luminous display apparatuses of which enlargement is simpler than any other display apparatus, the PDP apparatuses are gaining popularity as display apparatuses and are replacing CRTs.
The PDP apparatus generates a gas discharge between electrodes by a direct current (DC) voltage or an alternating current (AC) voltage which are supplied to the electrodes. Here, ultraviolet light is generated. Then, a phosphor is excited by ultraviolet light, thereby emitting light. However, the PDP apparatus has a defect in that an amount of emitted electromagnetic (EM) radiation and near infrared (NI) radiation with respect to a driving characteristic is great, surface reflectivity of the phosphor is great, and color purity due to orange light emitted from helium (He), or xenon (Xe) used as a sealing gas is lower than the CRT. Accordingly, EM radiation and NI radiation generated in the PDP apparatus may have harmful effects on human bodies, and cause sensitive equipment such as wireless telephones, remote controls, and the like, to malfunction.
Therefore, in order to use the PDP apparatus, it is required to prevent emission of EM radiation and NI radiation emitted from the PDP apparatus from increasing to more than a predetermined level. PDP filters having functions such as an EM radiation-shielding function, an NI radiation-shielding function, a surface antiglare function, enhancement of color purity, and the like, are used for EM radiation-shielding and NI radiation-shielding while simultaneously reducing reflected light, and enhancing color purity.
However, since each functional film realizing the above-described functions which is applied to the PDP filter has a given structure and a given material, optical properties unrelated to external environmental causes are exhibited. As a result, various demands depending on an environment of the display apparatus while in use cannot be satisfied.